Many of the features of the Artificer's Armorer subclass published in Tasha's Cauldron directly impact their armor, and I have had a few questions on how these features would work in relation to magic armors.
The stack has already established that the level 3 feature Arcane Armor does indeed work on magic armors, so I am moving to the next one : Armor modifications
That feature describes that:
At 9th level, you learn how to use your artificer infusions to specially modify your Arcane Armor. That armor now counts as separate items for the purposes of your Infuse Items feature: armor (the chest piece), boots, helmet, and the armor's special weapon
My question on that feature has to do with the Artificer's Infusion feature, that specifies that it works only on mundane items.
Because of that, my interpretation was that while you could use a magic armor for your arcane armor feature, it would mean that you would be unable to put infusions on it even when reaching 9th level, since the "magic property" of your armor would be carried over to each of the armor parts.
However while searching the web, I found many people arguing otherwise, and am now unsure about my reasoning.
Does the armor modification feature make you able to infuse the "extra" parts (e.g. boots or weapon) of your magic Arcane armor, or does the "magic" property of the armor carry over on those parts and make you unable to do so?